This trial will be a Phase I Open Label, Placebo-controlled Dose Escalation Study to Evaluate Safety and Pharmacokinetics of Natrunix via Subcutaneous Injection in Healthy Subjects. The target enrollment is 8 healthy subjects per cohort (including six for Natrunix and two for placebo). Three cohorts for a total of 24 healthy volunteers.

Study Title: A Phase I Open Label, Placebo-controlled Dose Escalation Study to Evaluate Safety and Pharmacokinetics of Natrunix via Subcutaneous Injection in Healthy Subjects.

Sponsor: XBiotech USA, Inc.

Study Chair: Neha Reshamwala, MD

Number of Planned Subjects: Eight healthy subjects per cohort (including six for Natrunix and two for placebo). Three cohorts for a total of 24 healthy volunteers.

Approximate Duration: Approximately 38 days for each subject which includes a screening period of up to 10 days followed by one subcutaneous dose of Natrunix, and then evaluation over 28 days. Blood will be sampled at various time points for blood chemistry, hematological analysis and Natrunix serum/plasma concentrations.

Inclusion Criteria:

1. Age: ≥ 18

2. Adequate bone marrow function defined as:

   • absolute neutrophil count (neutrophil and bands) of ≥ 1,500/mm3 (≥ 1.5 x 109/L)
   • platelet count > 150,000/mm3
   • hemoglobin of ≥ 10 g/dL

3. Adequate renal function, defined by serum creatinine ≤ 1.5 x lab ULN.

4. Adequate hepatic function defined as:

5. serum albumin ≥ 3.0 g/dL

6. total bilirubin ≤ 1.5 times lab ULN.

7. alanine aminotransferase (ALT) ≤ 2.0 times lab ULN.

8. aspartate aminotransferase (AST) ≤ 2.0 times lab ULN

9. For WOCBP, a negative pregnancy test at screening. For subjects with reproductive potential, willingness to use one method of contraception of high efficacy during the entire study period. These methods can include but not limited to hormonal contraceptives, intrauterine devices, condoms, diaphragms etc. Women of non-childbearing potential include those considered to have a medical history that indicates that pregnancy is not a reasonable risk, including post-menopausal women and those with a history of hysterectomy or surgically sterilized.

10. If the participant is a male participating in this clinical research study, the subject should not get a sexual partner pregnant during participation in this research study as the effect of the study drug on sperm is not known. The male contraception methods can include but not limited to mechanical methods (abstinence, withdrawal, non-vaginal intercourse) or contemporary methods comprising condoms and vasectomy.

11. Signed and dated Institutional Review Board (IRB) approved informed consent before any protocol-specific screening procedures are performed.

Exclusion Criteria:

1. Treatment with any biologicals (including intravenous immunoglobulin) or investigational agents within the last 4 weeks (or 5 half-lives, whichever is longer).

2. Uncontrolled or significant cardiovascular disease, including:

   • A myocardial infarction within the past 6 months.
   • Uncontrolled angina within the past 3 months.
   • Congestive heart failure within the past 3 months, defined as New York Heart Association (NYHA) Class II or higher.
   • Uncontrolled hypertension (blood pressure >160 mm Hg systolic or >100 mm Hg diastolic).

3. Dementia or altered mental status that would prohibit the understanding or rendering of informed consent.

4. Treatment with immunosuppressant agents, including corticosteroids or cyclosporine within the last 4 weeks.

5. Serious uncontrolled medical disorders, such as uncontrolled diabetes, active peptic ulcer disease, cerebrovascular accident within three months, ongoing congestive heart failure, and any other condition, which in the opinion of the investigator, would put the subject at risk by participating in the trial.

6. History of severe allergic or anaphylactic reactions to humanized or murine monoclonal antibodies.

7. Abnormal ECG with any clinically significant findings or with QTc > 470 ms.

8. Infection requiring treatment with antibiotics within 3 weeks prior to screening.

9. Infectious disease:

   • Positive HIV, RPR, Hepatitis B or C, TB (QuantiFERON-TB Gold (QFT)/ IGRA)

10. History of immunodeficiency.

11. Female subjects who are pregnant, planning to become pregnant during the course of the study, or breast-feeding.

12. Major surgery within 28 days prior to Day 0.

13. History of progressive multifocal leukoencephalopathy (PML) or other demyelinating disease.

No It is not yet known if there will be a plan to make IPD available